From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Summer 2001, No. 3


Growers who consistently produce high yields know how to integrate many production factors in an attempt to optimize crop growth. An important part of this integration process is balanced nutrition…supplying nitrogen, phosphorus, and potassium, plus any needed secondary or micronutrients, in sufficient quantities so nutrition does not limit plant growth at any time during the season.

Of all the plant essential nutrients…and there are 17 of them…potassium stands out as the single nutrient most effective in reducing pest problems. Researchers have documented reductions in fungal diseases, viruses, nematodes, insect and mite infestation, and bacterial disorders by potassium. This, of course, results in higher yields and better quality.

Why is potassium so effective in reducing so many pest problems? There is no simple or single answer. But it is likely related to the fact that potassium is involved in dozens of essential processes in the plant. Potassium plays a role in activating many enzyme systems …at least 60 different enzymes that are involved in plant growth. This alone explains why so many different plant processes depend on potassium. Seemingly, if it occurs within the plant, then potassium is involved...directly or indirectly.

Specific benefits of potassium include:

Protein synthesis — Without adequate potassium, nitrogen raw materials such as amino acids and nitrate accumulate in the plant. Regardless of how much nitrogen is applied, plants cannot convert that nitrogen into protein. This leads to low quality grain and forage.

Carbohydrate synthesis — Photosynthesis is affected by potassium nutrition. So when potassium is low, photosynthesis is slowed. This means that the production of carbohydrates…the end-product of photosynthesis…is also slowed. This directly reduces the quality of many crops, including grapes, sugarbeets, potatoes, and stone fruits.

Carbohydrate transport — Once produced, the carbohydrates must be transported to other parts of the plant for utilization or storage. This process requires energy that is provided in the form of ATP…adenosine triphosphate. Optimum production of ATP is dependent on adequate supplies of potassium.

Starch synthesis Carbohydrates are stored in the plant in the form of starch. Without adequate potassium, soluble carbohydrates are not converted to starch. Perennial crops, such as alfalfa, are more subject to winter-kill without sufficient root reserves of starch.

Efficient water use Plants depend on potassium to regulate the opening and closing of stomates…the pores through which leaves exchange carbon dioxide, water vapor, and oxygen. When potassium is deficient, the stomates become sluggish and closure may take hours rather than minutes, making the plants more susceptible to water stress.

Well-nourished plants fight disease and insects much more effectively than those suffering stress. By producing a strong, vigorously growing plant, fertilizer contributes to the overall plant well-being…a holistic approach to pest control. This is not to say that pests can be controlled through nutrition alone. However, it is well-documented that effects of pests can be significantly reduced, which leads to reduced pesticide use and more economical production. And potassium leads the way in using nutrients to reduce pests…the holistic way.

— AEL —

For more information, contact Dr. Albert E. Ludwick, Western Director, PPI, P.O. Box 970, Bodega Bay, CA 94923. Phone: (707) 875-2163. E-mail:
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